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17 March 2006 How does mass lesion detection vary with display window width and radiation exposure in computed radiography?
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In this study, we investigated lesion detection using a computed radiography (CR) imaging system in the absence of any anatomical background. Parameters investigated were the lesion size, display window width, and radiation exposure. Uniform CR exposures were obtained for an air kerma at the receptor between approximately 1 μGy and 10 μGy, which are typical values for radiographic imaging. We added simulated spherical lesions ranging from 1 to 5.5 mm. Observer detection performance was measured using a 4 Alternate Forced Choice (4-AFC) method that determines the lesion intensity (contrast) needed to achieve 92% accuracy (I92%). We generated contrast detail curves (I92% vs lesion size) for the various radiation doses, and display contrast settings that were varied by a factor of approximately eight. All contrast-detail curves showed a linear relationship between detection threshold intensity (I92%) and lesion size. Measured contrast detail slopes were -0.65 at 1 μGy, and -0.71 at 10 μGy. Increasing the radiation exposure by a factor of ten improved detection of 1 mm size lesions by a factor of 2.25 and 5.5 mm lesions by a factor of 1.8. Decreasing display contrast by a factor of four reduced lesion visibility by ~25% for exposures > 5 μGy, and by ~10% for exposures of 1 μGy. Reductions in lesion visibility with lower display contrast were similar for all lesion sizes. Detection performance generally improves when the radiation dose and/or display contrast are increased. At the lowest radiation dose (1 μGy), display contrast is less important than at doses above 5 μGy.
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K. M. Ogden, W. Huda, V. Garg, M. Khan, M. A. Reichel, and M. L. Roskopf "How does mass lesion detection vary with display window width and radiation exposure in computed radiography?", Proc. SPIE 6146, Medical Imaging 2006: Image Perception, Observer Performance, and Technology Assessment, 614611 (17 March 2006);

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